Diaphragm pump

ABSTRACT

A diaphragm pump is provided. The diaphragm includes an upper housing, a diaphragm, and a lower housing. Recessed parts are formed in the surfaces of the upper and lower housings that face the diaphragm to define an upper pump chamber and a lower pump chamber above and below the diaphragm. A suction port and a discharge port are formed in the lower housing to communicate with the lower pump chamber. Branch channels are formed in the lower housing and the upper housing to communicate the suction port and the discharge port with the upper pump chamber. Suction-side check valves are respectively provided between the suction port and the upper pump chamber and between the suction port and the lower pump chamber. Discharge-side check valves are provided between the discharge port and the upper pump chamber and between the discharge port and the lower pump chamber.

This application claims the benefit of Japanese Patent Application No.2005-280548 filed on Sep. 27, 2005 and Japanese Patent Application NO.2006-136693 filed on May 16, 2006.

BACKGROUND

1. Field

The present embodiments relate to a diaphragm pump.

2. Related Art

A diaphragm pump, as disclosed in, for example, Japanese UnexaminedPatent Application Publication No. 11-182413, is configured such that apump chamber (variable volume chamber) is formed by a diaphragm. A pairof flow channels connected with the pump chamber is provided with a pairof check valves, which are different in the direction of flow (asuction-side check valve, which allows the flow of fluid to the pumpchamber, and a discharge-side check valve, which allows the flow offluid from the pump chamber). When the diaphragm is vibrated, since thevolume of the pump chamber changes, and the operation of opening thesuction-side check valve during the stroke in which the volumeincreases, and the operation of opening the discharge-side check valveduring the stroke in which the volume reduces, are repeated, a pumpingaction is obtained. The diaphragm is made of elastic (vibrational)materials, for example, rubber and piezoelectric vibrator.

In this diaphragm pump, as described above, since the operation ofopening the suction-side check valve during the stroke in which thevolume of the pump chamber increases, and the operation of opening thedischarge-side check valve during the stroke in which the volumereduces, are repeated, pulsation in the discharge port is inevitable.

A diaphragm pump with half the cycle of the pulsation has been disclosed(Japanese Patent Application No. 2004-154991). According to thisdiaphragm pump, an upper pump chamber and a lower pump chamber (a pairof pump chambers) are respectively formed above and below a diaphragm bythe diaphragm. A single suction port and a single discharge port areprovided. First and second suction-side check valves, which allow theflow of fluid from the suction port to the pair of pump chambers and donot allow the flow of fluid in the reverse direction are providedbetween the pair of pump chambers, and the suction port. First andsecond discharge-side check valves, which allow the flow of fluid fromthe pair of pump chambers to the discharge port and do not allow theflow of fluid in the reverse direction are provided between the pair ofpump chambers and the discharge port (4-valve diaphragm pump).

The 4-valve diaphragm pump can basically be configured by formingrecessed parts, which define an upper pump chamber and a lower pumpchamber, in upper and lower housings, which sandwich a diaphragm,stacking these housings in order, and forming flow channels whichcommunicates a pair of pump chambers and the suction and dischargesports, in the upper and lower housings. However, there is a need for a4-valve diaphragm pump that ensures liquid tightness of connecting partsof the flow channels formed over the upper housing and the lower housingor the liquid tightness of the suction flow channel and the dischargeflow channel, with high reliability and durability.

SUMMARY

One exemplary object of the present embodiments is to provide a 4-valvediaphragm pump that is liquid tight at the connecting parts of flowchannels formed over an upper housing and a lower housing. A secondexemplary object of the present embodiments is to provide a 4-valvediaphragm pump capable of ensuring the liquid tightness of a suctionflow channel and a discharge flow channel with high reliability anddurability.

In a present embodiment, a diaphragm pump includes an upper housing, adiaphragm, and a lower housing which are stacked in order. Recessedparts are respectively formed in the surfaces of the upper and lowerhousings facing the diaphragm to define an upper pump chamber and alower pump chamber above and below the diaphragm. A suction port and adischarge port are formed in the lower housing to communicate with thelower pump chamber. Branch channels are formed in the lower housing andthe upper housing to communicate the suction port and the discharge portwith the upper pump chamber. Suction-side check valves are respectivelyprovided between the suction port and the upper pump chamber and betweenthe suction port and the lower pump chamber. Discharge-side check valvesare respectively provided between the discharge port and the upper pumpchamber and between the discharge port and the lower pump chamber. Thebranch channels include holes formed in either the upper housing or thelower housing, a protruding cylindrical part fitted into the hole, and asealing ring disposed in an annular gap formed between the hole and theprotruding cylindrical part such that a compressive force is generatedradially.

Although the upper housing can theoretically be composed of one member,it is practical that the upper housing is composed of two members in acase where the upper housing is a molded article made of a resinmaterial. If the upper housing is composed of two members, a problemoccurs in the structure in which the liquid tightness of the suctionflow channel and the discharge flow channel is ensured. The presentembodiments disclose a suitable liquid-tight structure in a case wherethe upper housing is composed of two members.

In a present embodiment, the upper housing is composed of two members.The upper housing is composed of a pump chamber plate, which is stackedon the diaphragm and has a recessed part for forming an upper pumpchamber and a blind plate stacked on the pump chamber plate. A pair ofan inter-plate suction flow channel and an inter-plate discharge flowchannel, which communicates the suction port and the discharge port withthe upper pump chamber, and which constitute parts of the branchchannels is formed between the pump chamber plate and the blind plate.The inter-plate suction flow channel and the inter-plate discharge flowchannel includes a pair of protruding parts formed in any one of thepump chamber plate and the blind plate, a pair of recessed groove partswhich are formed in the other one of the pump chamber plate and theblind plate to allow the pair of protruding parts to fit thereinto, anda pair of sealing rings which are disposed in a pair of closed curvegaps between the pair of protruding parts and the pair of recessedgroove parts such that a compressive force is generated radially.

In another embodiment, the upper housing is composed of two members. Theupper housing is composed of an upper plate, which is stacked on thediaphragm and a pair of lid plates that are members separate from theupper plate. The upper plate is formed with recessed parts, which areopened to the front and back of the upper plate to form the upper pumpchamber, and a pair of an open suction flow channel groove and an opendischarge flow channel groove which communicates with the suction portand the discharge port with the upper pump chamber. Any one of the upperplates and the pair of lid plates is formed with protruding partscorresponding to the open suction flow channel groove and the opendischarge flow channel groove. The other one of the upper plates and thepair of lid plates is formed with recessed groove parts to allow thepair of protruding parts to fit thereinto. A pair of sealing rings areinterposed between the protruding parts and the recessed groove partssuch that a compressive force is generated radially.

In one exemplary embodiment, the protruding parts, the recessed grooveparts, and the sealing rings are elliptical.

By keeping a compressive force in the stacked direction of the upperhousing, the diaphragm, and the lower housing from being applied to anyof the sealing rings, and allowing a compressive in a direction (radialdirection) orthogonal to the stacked direction to be applied to thesealing rings, the liquid tightness can be ensured with high durability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exploded state showing one exemplaryembodiment of a diaphragm pump;

FIG. 2 is a sectional view of the exploded state according to FIG. 1;

FIG. 3 is a plan view of an exemplary lower housing;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

FIG. 5 is a sectional view taken along line V-V of FIG. 3;

FIG. 6 is a plan view of an upper housing on the side of a pump chamberplate;

FIG. 7 is a plan view of the pump chamber plate on the side of arecessed part for forming a pump chamber;

FIG. 8 is an exploded perspective view of a bimorph-type piezoelectricvibrator;

FIG. 9 is a perspective view showing the relationship between thebimorph-type piezoelectric vibrator and a modified D-type sealing ring;

FIG. 10 is a plan view of principal parts of the piezoelectric vibrator;

FIGS. 11A and 11B are conceptual diagrams, in different vibratingdirections, of a diaphragm of a 4-valve diaphragm pump to which the oneexemplary embodiment is applied;

FIG. 12 is a perspective view showing another embodiment, including asection corresponding to FIG. 4;

FIG. 13 is an enlarged sectional view of principal parts of theembodiment of FIG. 12;

FIG. 14 is a perspective view that illustrates a blind plate of theembodiment of FIG. 12.

FIG. 15 is a perspective view showing still another embodiment,including a section corresponding to FIG. 4;

FIG. 16 is an enlarged sectional view of principal parts of theembodiment of FIG. 15; and

FIG. 17 is an enlarged perspective view of the principal parts of theembodiment of FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Illustrated embodiments are obtained by applying the present embodimentsto a 4-valve diaphragm pump that the present applicant proposed theprinciple in Japanese Patent Application No. 2004-154991. One embodimentthereof will be described with reference to FIGS. 1 to 7. In oneexemplary embodiment, the diaphragm pump has an upper housing 10, alower housing 20, and a piezoelectric vibrator 30, and is in the shapeof a flat rectangular parallelepiped as a whole. The upper housing 10 iscomposed of a blind plate 101 and a pump chamber plate 102, and all theblind plate 101, the pump chamber plate 102, and the lower housing 20are molded articles made of a resin material.

The lower housing 20 is a member in the shape of a flat rectangularparallelepiped, which is most large-sized and has a complicate shape,among the molded articles. In the lower housing, a recessed part 20 afor forming a pump chamber is formed so as to be open to the sideopposing the piezoelectric vibrator 30, and a suction port 31 and adischarge port 32, which are molded integrally and parallel to eachother, are formed so as to protrude from one surface of flat peripheralfour surfaces of the lower housing (refer to FIGS. 1 to 5).

The lower housing 20 is formed with a suction-side flow channel 24Hcommunicating with the suction port 31, and a discharge-side flowchannel 25D communicating with the discharge port 32. Inner ends of thesuction-side flow channel 24H and the discharge-side flow channel 25Dare respectively formed with flow channel enlarged parts 24Ha and 25Dacommunicating with the recessed part 20 a for forming a pump chamber.Valve-receiving recessed parts 24Hb and 25Db are respectively formed atthe ends of the flow channel enlarged parts 24Ha and 25Da on the side ofthe recessed part 20 a for forming a pump chamber.

A suction-side umbrella unit (suction-side check valve unit) 21U and adischarge-side umbrella unit (discharge-side check valve unit) 22U areadhesively fixed to the valve-receiving recessed parts 24Hb and 25Db,respectively. The suction-side umbrella unit 21U and the discharge-sideumbrella unit 22U have the same structure except that their mountingdirections are different from each other. A central part of a unit plate21 a (unit plate 22 a) whose peripheral edge serves as an adhesive joint21 b (adhesive joint 22 b) to be adhered to the valve-receiving recessedpart 24Hb (valve-receiving recessed part 25Db) is formed with anumbrella mounting hole 21 c (umbrella mounting hole 22 c), and aperipheral edge of the umbrella mounting hole 21 c (umbrella mountinghole 22 c) is formed with a plurality of flow channel holes 21d (flowchannel holes 22 d).

An umbrella part 21 g (umbrella part 22 g) of an umbrella 21 f (umbrella22 f) whose central shaft 21 e (central shaft 22 e is mounted into theumbrella mounting hole 21 c (umbrella mounting hole 22 c) plugs up theflow channel holes 21 d (flow channel holes 22 d) normally. When apressure beyond a rated value is applied to the umbrella part 21 g(umbrella part 22 g) from the flow channel holes 21 d (flow channelholes 22 d) side, the umbrella part 21 g (umbrella part 22 g) deformselastically, and thus the flow channel holes 21 d (flow channel holes 22d) are opened.

In the suction-side umbrella unit 21U or the discharge-side umbrellaunit 22U, the adhesive joint 21 b (22 b) is adhesively fixed to thevalve-receiving recessed part 24Hb or 25Db, with their front and backreversed. The suction-side umbrella unit 21U allows the flow of fluidfrom the suction port 31 to the recessed part 20 a for forming a pumpchamber (pump chamber 23), and does not allow the flow of fluid reversethereto, and the discharge-side umbrella unit 22U allows the flow offluid from the recessed part 20 a for forming a pump chamber (pumpchamber 23) to the discharge port 32, and does not allow the flow offluid reverse thereto. The unit plates 21 a and 22 a of the suction-sideand discharge-side umbrella units 21U and 22U may be formed as onesubstrate.

The lower housing 20, which is a single body that does not require a lidas a separate body, is formed with the suction-side flow channel 24H andthe discharge-side flow channel 25D, which are closed between thesuction port 31 and the recessed part 20 a for forming a pump chamberand between the discharge port 32 and the recessed part 20 a for forminga pump chamber. The lower housing 20 is formed with a sealing ringgroove 20 b, which is located around the recessed part 20 a for forminga pump chamber. The sealing ring groove 20 b is in the shape of amodified letter “D” having a large circular-arc part 20 b 1 that is apartial circle larger than a semicircle, and a straight part 20 b 2whose connects both ends of the large circular-arc part 20 b 1 togetherby a straight line.

The suction-side umbrella unit 21U and the discharge-side umbrella unit22U, i.e., the valve-receiving recessed parts 24Hb and 25Db (umbrellaparts 21 g and 22 g) are inclined (non-parallel) with respect to theplane of a piezoelectric vibrator 300. When a plane orthogonal to thepiezoelectric vibrator 30, including the axis of the suction port 31(discharge port 32), is considered, the inclined direction is adirection in which the plane is separated apart from the piezoelectricvibrator 30 as it goes toward the inner end of the suction port 31(discharge port 32) and approaches the piezoelectric vibrator as it goesto the near side. If the suction-side umbrella unit 21U and thedischarge-side umbrella unit 22U are inclined in this way, the lowerhousing 20 can be made thin without sacrificing the channel sectionalarea of the suction port 31 and the discharge port 32.

For example, as shown in FIG. 4, the surface (unit plate 21 a (umbrellapart 21 g) of the suction-side umbrella unit 21U) of the valve-receivingrecessed part 24Hb and the plane of the piezoelectric vibrator 30 in afree state, which are non-parallel, forms an angle α. A flow channel ina suction-side check valve (suction-side umbrella unit 21U) is notorthogonal to the piezoelectric vibrator 30. The axis of the suctionport 31 (suction-side flow channel 24H) is parallel to the plane of thepiezoelectric vibrator 30. The direction of the angle α is a directionin which the unit plate 21 a (umbrella part 21 g) of the suction-sideumbrella unit 21U is separated from the piezoelectric vibrator 30 as itgoes toward the inner end (left side of FIG. 4) of the suction port 31(suction-side flow channel 24H), and approaches the piezoelectricvibrator 30 as it goes to the near side (right side of FIG. 4).

As shown in FIG. 5, the surface (unit plate 22 a (umbrella part 22 g) ofthe discharge-side umbrella unit 22U) of the valve-receiving recessedpart 24Db and the plane of the piezoelectric vibrator 30 in a freestate, which are non-parallel, forms an angle α. For example, a flowchannel in a discharge-side check valve (discharge-side umbrella unit22U) is not orthogonal to the piezoelectric vibrator 30. The axis of thedischarge port 32 (discharge-side flow channel 24D) is parallel to theplane of the piezoelectric vibrator 30. The direction of the angle α isa direction in which the unit plate 22 a (umbrella part 22 g) of thedischarge-side umbrella unit 22U is separated from the piezoelectricvibrator 30 as it goes toward the inner end (left side of FIG. 5) of thedischarge port 32 (discharge-side flow channel 25D), and approaches thepiezoelectric vibrator 30 as it goes to the near side (right side ofFIG. 5).

The lower housing 20 is further formed with branch channels 24Hd and25Dd, which branch from the suction-side flow channel 24H and thedischarge-side flow channel 25D, and which are opened toward the pumpchamber plate 102 (upper housing 10). The pump chamber plate 102 isformed with communicating holes (branch channel) 41 and 42 communicatingwith the branch channels 24Hd and 25Dd. An inter-plate suction flowchannel 14H and an inter-plate discharge flow channel 15D communicatingwith the communicating holes 41 and 42, are formed between the blindplates 101 and the pump chamber plate 102 which constitute the upperhousing 10. For example, the pump chamber plate 102 is formed withprotruding cylindrical parts 41 a and 42 a which fit into the branchchannels 24Hd and 25Dd, and the communicating holes 41 and 42 are formedin the centers of the protruding cylindrical parts 41 a and 42 a.

Open ends of the branch channels 24Hd and 25Dd of the lower housing 20are respectively formed with large-diameter stepped parts 24He and 25De,which have a larger diameter than the outer diameter of the protrudingcylindrical parts 41 a and 42 a. When the protruding cylindrical parts41 a or 42 a are fitted into branch channels 24Hd or 25Dd, as shown inFIGS. 4 and 5, an annular gap 41 c or 42 c is formed between theprotruding cylindrical part 41 a or 42 a, and the large-diameter steppedpart 24He or 25De. An O-ring (sealing ring) 41 b or 42 b is insertedinto the annular gap 41 c or 42 c.

The inner diameter of the O-ring 41 b or 42 b is set to be smaller thanthe outer diameter of the protruding cylindrical part 41 a or 42 a, andthe outer diameter thereof is set to be greater than the large-diameterstepped part 24He or 25De. The O-ring is kept in a state where it isbrought into close contact with the protruding cylindrical part 41 a or42 a and large-diameter stepped part 24He or 25De, thereby generatingcompressive force in its radial direction. For example, the O-ring 41 bor 42 b keeps a space between the branch channel 24Hd or 25Dd and theprotruding cylindrical part 41 a or 42 a (communicating hole 41 or 42)liquid-tight.

The length (thickness) d1 (FIG. 4 or FIG. 5) of the annular gap 41 c or42 c in the stacked direction is set to be greater than the thickness(diameter of a section) of the O-ring 41 b or 42 b. This length d1 isensured uniformly. For example, when the protruding cylindrical parts 41a and 42 a are respectively inserted into the branch channels 24Hd and25Dd, an entrance regulating surface 41 d or 42 d of the pump chamberplate 102 abuts on an abutting surface 24Hi or 25Di, which faces theentrance regulating surface 41 d or 42 d. The insertion (entrance)position of the protruding cylindrical part 41 a or 42 a is regulated.The O-ring 41 b or 42 b does not receive a compressive force in thestacked direction from the lower housing 20 and the pump chamber plate102. Any force that makes the lower housing 20 and the pump chamberplate 102 separated in the stacked direction from the O-rings 41 b and42 b is not applied to the lower housing and the pump chamber plate.

Since a compressive force that is uniform as a whole is applied to thepiezoelectric vibrator 30 from the stacked direction, vibration of thepiezoelectric vibrator 30 is also uniformly generated in the stackeddirection. The operation of the piezoelectric vibrator 30 can bestabilized, and a fluid can be generated efficiently.

The surface of the pump chamber plate 102, which faces piezoelectricvibrator 30 becomes a recessed part 40 a for forming a pump chamber(FIGS. 2, 4, and 5). A substantially central part of the pump chamberplate is mounted with a suction-side umbrella 11 and a discharge-sideumbrella 12 respectively corresponding to the suction-side umbrella unit21U and the discharge-side umbrella unit 22U. The suction-side umbrella11 and the discharge-side umbrella 12 are not drawn on FIG. 2. Forexample, in the positions vertically corresponding to the suction-sideumbrella unit 21U and the discharge-side umbrella unit 22U, the pumpchamber plate 102 is formed with umbrella mounting holes 11 a and 12 a.The peripheral edges of the umbrella mounting holes 11 a and 12 a arerespectively formed with a plurality of flow channel holes 11 b or 12 b.

The suction-side umbrella 11 or the discharge-side umbrella 12 has acentral shaft 11 c (central shaft 12 c), which is mounted to theumbrella mounting hole 11 a (umbrella mounting hole 12 a), and anumbrella part 11 d (umbrella part 12 d) which plugs up the flow channelholes 11 b (flow channel holes 12 b) normally. When a pressure beyond arated value is applied to the umbrella part 11 d (umbrella part 12 d)from the flow channel holes 11 b (flow channel holes 12 b) side, theumbrella part 11 d (umbrella part 12 d) deforms elastically to open theflow channel holes 11 b (flow channel holes 12 b).

The suction-side umbrella 11 allows the flow of fluid from the blindplate 101 side to the recessed part 40 a for forming a pump chamber(pump chamber 13), and does not allow the flow of fluid reverse thereto,but the discharge-side umbrella 12 allows the flow of fluid from therecessed part 40 a for forming a pump chamber (pump chamber 13) to theblind plate 101 side, and does not allow the flow of fluid reversethereto.

The blind plate 101 has substantially the same planar shape as the lowerhousing 20 so as to overlap the lower housing 20. The blind plate 101 isformed with a recessed part 14Ha, which forms an inter-plate suctionflow channel 14H that communicates a communicating hole 41 with thesuction-side umbrella 11, and a recessed part 15Da for forming aninter-plate discharge flow channel 15D that communicates a communicatinghole 42 with the discharge-side umbrella 12, between itself and the pumpchamber plate 102 (refer to FIG. 2 and FIGS. 4 to 6). Sealing ringgrooves 14Hb and 14Dc for allowing elliptical O-rings (sealing rings)15Da and 15Da to be fitted thereinto are formed around the recessedparts 14Ha and 15Da, respectively. The blind plate 101 is also formedwith a recessed part 10 a (FIGS. 2 and 6) for allowing the pump chamberplate 102 to be fitted thereinto.

The pump chamber plate 102 and the blind plate 101 are respectivelyformed with positioning fitting protrusions 40 c and fitting holes 10 c(FIG. 1) which are fitted to each other in a state where the ellipticalO-ring 14Hb and 15Db are fitted into the recessed parts 14Ha and 15Da,for example, respectively. By bonding the positing fitting protrusionsand the fitting holes together after they are fitted to each other, theliquid-tight inter-plate suction flow channel 14H that is liquid-tightfrom the communicating hole 41 to the suction-side umbrella 11 and theinter-plate discharge flow channel 15D which is liquid-tight from thedischarge-side umbrella 12 to the communicating hole 42 are formed. Forexample, the positioning fitting protrusions 40 c are fitted into therecessed parts 10 a, for example, respectively, so that the blind plate101 and the pump chamber plate 102 may be integrated in advance, therebyforming the inter-plate suction flow channel 14H and the inter-platedischarge flow channel 15D which are closed therebetween. Lid membersother than the blind plate 101 and the pump chamber plate 102 in formingthe inter-plate suction flow channel 14H and the inter-plate dischargeflow channel 15D are not needed.

As shown in FIG. 7, a sealing ring groove 40 b corresponding to (havingthe same shape in plan view) the sealing ring groove 20 b of the lowerhousing 20 is formed around the recessed part 40 a for forming a pumpchamber, which faces the piezoelectric vibrator 30, in the pump chamberplate 102. The sealing ring groove 40 b is in the shape of a modifiedletter “D” having a large circular-arc part 40 b 1 that is a partialcircle larger than a semicircle, and a straight part 40 b 2 whoseconnects both ends of the large circular-arc part 40 b 1 together by astraight line.

Both of a unimorph-type piezoelectric vibrator and a bimorph-typepiezoelectric vibrator can be used as the piezoelectric vibrator 30.FIGS. 8 to 10 are schematic views of one embodiment of the bimorph-typepiezoelectric vibrator, which is proposed in Patent Application No.2004-192483 by the present applicant. This piezoelectric vibrator isprovided with a circular shim 111 at the central part thereof, andpiezoelectric elements 112 which are stacked on the front and backthereof. The shim 111 is made of a conductive metallic thin platematerial, for example, a stainless steel thin plate having a thicknessof about 0.2 mm.

The piezoelectric elements 112 are made of, for example, PZT (Pb(Zr,Ti)O₃) having a thickness of about 3 mm, and they are subjected topolarizing treatment in the direction of the front and back thereof.This polarizing treatment is performed in the same direction in the pairof piezoelectric elements 112 located at the front and back of the shim111. For example, referring to FIG. 8, when the polarization directionof the pair of piezoelectric elements 112 are denoted by arrow “a” or“b”, the polarizing treatment in the same direction as the thicknessdirection of the shim 111 is performed. The pair of front and backpiezoelectric elements 112 in contact with the shim 111 exhibitspolarization characteristics of different poles, respectively, and theexposed surfaces of the pair of piezoelectric elements 112 becomedifferent poles, respectively. If the front and back piezoelectricelements 112 are allowed to have the polarization characteristic of thesame direction in this way, the displacement of the shim 111 can beincreased when positive and negative voltages are applied alternatelybetween the shim 111 and the exposed surfaces of the pair ofpiezoelectric elements 112 at the front and back of the shim 111.

The whole surfaces of the piezoelectric elements 112 on the side of thepair of shims 111 are adhered to the shim 111 so as to be electricallyconnected thereto, and a filmy electrode 113 is formed on each of thewhole exposed surfaces of the piezoelectric elements opposite to theshim 111. The filmy electrode 113 is formed, for example, by printing(screen-baking) conductive paste (silver paste).

A power supply terminal 180 has a pair of contactors 1811, a connectionline 1812 which connects the contactors 1811 to each other, and a wiringconnection 1813. The pair of contactors 1811 and the connection line1812 forms a U-shaped section. The pair of contactors 1811 has the sameconfiguration having a substantially triangular part in plan view thatis broader on the side of the wiring connection 1813 located outside thepiezoelectric vibrator 30, and becomes gradually narrower toward thecentral part of the piezoelectric vibrator 30. For example, eachcontactor 1811 is the narrowest on the side of a part 1131 soldered tothe filmy electrode 113 of the piezoelectric vibrator 30, and increasesin width toward the outside of the piezoelectric vibrator 30.

A wiring connecting projection 114, which is formed in the shim 111 ofthe piezoelectric vibrator 30 and projects in the radial directionextends between the pair of contactors 1811. This wiring connectingprojection 114 is formed with an insulating recessed part 1141, whichensures a gap from the connection line 1812 that connects the pair ofcontactors 1811 to each other.

A pair of annular spacer insulating rings 115 are located above andbelow the circular shim 111, for example, respectively, and stripedinsulating plate materials 1151 extends to between the pair ofcontactors 1811 and the wiring connecting projection 114 from the pairof spacer insulating rings 115 so that the short-circuiting between theshim 111 and the power supply terminal 180 can be prevented. Eachstriped insulating plate material 1151 prevents the connection line 1812of the power supply terminal 180 from moving toward the insulatingrecessed part 1141 of the shim 111, thereby ensuring insulation.

The wiring connecting projection 114 of the shim 111 is formed with apair of lead wire latching recessed parts 1143 and 1144 which arelocated further outside the piezoelectric vibrator 30 than theinsulating recessed part 1141 and which are symmetrical with respect toeach other on both sides of the wiring connecting projection 114 in thewidth direction thereof, and a soldering through hole 1145 is formedinwardly from one lead wire latching recessed part 1143.

The wiring connection 1813 of the power supply terminal 180 is formedwith a soldering through hole 1814 corresponding to the solderingthrough hole 1145 of the wiring connecting projection 114. The solderingthrough holes 1145 and 1814 are different in positions in plan view, andsoldered to lead wires 211 and 221, for example, respectively. Since thesoldering through holes 1145 and 1814 increase soldering strength andare made different in positions in plan view, the whole diaphragm pumpcan be made thin. The lead wires 211 and 221 are hung on the lead wirelatching recessed parts 1143 and 1144, thereby increasing resistanceagainst falling-off of the lead wires 211 and 221.

A PPS film (insulating films) 116 (FIG. 8) is adhered to each surface ofthe piezoelectric vibrator 30. The PPS film 116 has a radial tonguepiece 116 a which extends onto the power supply terminal 180 to preventdisengagement between the contactors 1811 and the filmy electrode 113 ofthe piezoelectric vibrator 30.

According to the wiring structure in the vicinity of the wiringconnecting projection 114 of the shim 111 and the power supply terminal180 which have been described hitherto, wiring to the shim 111 and thefilmy electrode 113 can be surely attained without obstructing movementof the piezoelectric vibrator 30.

The piezoelectric vibrator 30 whose basic shape is a planar circularshape as described above is sandwiched between the recessed part 20 afor forming a pump chamber of the lower housing 20 and the recessed part40 a for forming a pump chamber of the pump chamber plate 102. The upperand lower peripheries of the piezoelectric vibrator are sealed with thesealing rings 16 and 26 to form the pump chambers 13 and 23. The sealingrings 16 and 26 have the same shape as the sealing ring groove 20 b ofthe lower housing 20 and the sealing ring groove 40 b of the pumpchamber plate 102, and have the large circular-arc part 16 a (largecircular-arc part 26 a) and the straight part 16 b (straight part 26 b).The power supply terminal 180 of the piezoelectric vibrator 30 islocated outside the sealing rings 16 and 26, i.e., outside the straightpart 16 b (straight part 26 b). Since this arrangement preventsintersection of the power supply terminal 180 to the piezoelectricelements 112 of the piezoelectric vibrator 30 with the sealing rings 16and 26 and local deformation of the sealing rings 16 and 26, thedurability can be improved.

The lower housing 20, and the blind plate 101 integrated in advance intothe pump chamber plate 102 are combined with each other and integratedinto one by fasteners (for example, bolt and nut), with thepiezoelectric vibrator 30 sandwiched between the lower housing and blindplate, as described above. In an alternate embodiment, an adhesive canbe used additionally.

In the diaphragm pump having the above configuration, when alternatingelectric fields are applied to between the power supply terminal 180 andthe shim 111 (wiring connecting projection 114) to elastically deform(vibrate) the piezoelectric vibrator 30 forward and backward, the volumeof one of the pump chambers 13 and 23 increases, and the volume of otherone decreases. During the stroke in which the volume of the pump chamber13 increases, since the suction-side umbrella 11 opens and a fluid flowsinto the pump chamber 13 from the suction port 31 and simultaneously thevolume of the pump chamber 23 decreases, the fluid in the pump chamber23 opens the discharge-side umbrella (unit) 22, and flows into thedischarge port 32.

During the stroke in which the volume of the pump chamber 13 decreases,since the suction-side umbrella (unit) 21 opens and a fluid flows intothe pump chamber 23 from the suction port 31, and the volume of the pumpchamber 13 decreases, the fluid in the pump chamber 13 opens thedischarge-side umbrella 12 and flows into the discharge port 32. Thecycle of the pulsation in the discharge port 32 can be shortened(reduced to half as compared with a case where a pump chamber is formedonly in one of the upper and lower sides of the piezoelectric vibrator30). Flow channels of the above-described 4-valve diaphragm pump areskeletonized in FIG. 1.

FIGS. 12 to 14 illustrate an alternate embodiment of the diaphragm pump.The present embodiment is configured such that, even in the sealstructure in the vicinity of the inter-plate suction flow channel 14Hand the inter-plate discharge flow channel 15D, which are formed betweenthe blind plate 101 and the pump chamber plate 102 (in the upper housing10), a force in the direction in which the blind plate 101 and areseparated from the pump chamber plate 102 is kept from being applied.

For example, instead of the sealing ring groove 14Hc and 15Dc, a pair ofrecessed groove parts 101 b 1 and 101 b 2 are respectively formed aroundthe recessed parts 14Ha and 15Da of the blind plate 101, as shown in theenlarged view of FIG. 13.The pump chamber plate 102 is formed with apair of elliptical protruding parts 101 b 1 and 102 b 1 which are causedto project toward the blind plate 101 and fit into a pair of recessedgroove parts 101 b 1 and 102 b 2, for example, respectively. When thepair of protruding parts 102 b 1 and 102 b 2 and the pair of recessedgroove part 101 b 1 and 101 b 2 are caused to fit into each other, apair of closed curve gaps 141 c and 142 c are formed therebetween.

Sealing rings 141 b and 142 b are inserted into the pair of closed curvegaps 141 c and 142 c, for example, respectively. When the sealing rings141 b and 142 b are inserted into the pair of closed curve gaps 141 cand 142 c, a compressive force is generated in the radial direction (thedirection in the plane of the blind plate 101 and the pump chamber plate102). For example, the spaces between the blind plate 101 and the pumpchamber plates 102 are held in liquid tightness by the sealing rings 141b and 142 b.

The length (thickness) d2 (FIGS. 12 and 13) of the pair of closed curvegaps 141 c and 142 c in the stacked direction of housings is set to begreater than the thickness (diameter of a section) of the sealing rings141 b and 142 b. This length d2 is ensured uniformly. For example, whenthe pair of protruding parts 102 b 1 and 102 b 2 are inserted into thepair of recessed groove parts 101 b 1 and 101 b 2, respectively,entrance regulating surfaces 102 a 1 and 102 a 2 of the pump chamberplate 102 abut on abutting surfaces 101 a 1 and 101 a 2, respectively,thereby regulating the insertion (entrance) position of the protrudingparts. The sealing rings 141 b and 142 b do not receive a compressiveforce in the stacked direction from the blind plate 101 and the pumpchamber plate 102. Any force that makes the blind plate 101 and the pumpchamber plate 102 separated in the stacked direction from the sealingring 141 b and 142 b is not applied to the blind plate and the pumpchamber plate. Since a compressive force that is uniform as a whole isapplied to the piezoelectric vibrator 30 from the stacked direction,vibration of the piezoelectric vibrator 30 is also uniformly generatedin the stacked direction. The operation of the piezoelectric vibrator 30can be stabilized, and a fluid can be generated efficiently.

FIGS. 15 to 17 show still another embodiment of the diaphragm pump. Thisembodiment is an embodiment in which the upper housing 10 is composed ofan upper plate 103 and a pair of lid plates 104H and 104D, a suctionflow channel 14H1 is formed between this upper plate 103 and the lidplate 104H, and a discharge flow channel 15D1 is formed between theupper plate 103 and the lid plate 104D.

Any force in the direction in which both are separated from each other(force in the direction in which the upper plate 103 and the lid plate104H (lid plate 104D) are separated from each other) is kept from beingapplied by the seal structure between the upper plate 103 and the lidplates 104H and between the upper plate 103 and the lid plate 104D. Forexample, the upper plate 103 is formed with an open suction flow channelgroove 103 b 1 and an open discharge flow channel groove 103 b 2 whosetop are opened. An inside end of the open suction flow channel groove103 b 1 is provided with an umbrella 11, and an outside end thereof isprovided with a branch channel 41.

Although not shown in FIG. 15, an inside end of the open discharge flowchannel groove 103 b 2 is provided with an umbrella 12, and an outsideend thereof is provided with a branch channel 42. Alternatively, thepair of lid plates 104H and 104D is provided with protruding parts 104 b1 and 104 b 2, respectively, which project toward the upper plate 103and fit into the open suction flow channel groove 103 b 1 and the opendischarge flow channel groove 103 b 2.

When the protruding parts 104 b 1 and 104 b 2 are caused to fit into theopen suction flow channel groove 103 b 1 and the open discharge flowchannel groove 103 b 2, respectively, closed curve gaps 241 c and 242 care formed therebetween, as shown in the enlarged view of FIG. 16. Thesealing rings 241 b and 242 b are inserted into the closed curve gaps241 c and 242 c, respectively, to form a liquid-tight suction flowchannel 14H1 and a liquid-tight discharge flow channel 15D1. When thesealing rings 241 b and 242 b are inserted into the pair of closed curvegaps 241 c and 242 c, respectively, a compressive force is generated inthe radial direction (the direction in the plane of the pair of lidplates 104H and 104D and the upper plate 103). For example, the spacesbetween the pair of lid plates 104H and 104D, and the upper plate 103are held in liquid tightness by the sealing rings.

The length d3 (FIGS. 15 and 16) of the closed curve gaps 241 c and 242 cin the stacked direction is set to be greater than the thickness(diameter of a section) of the sealing rings 241 b and 242 b. Thislength d3 is ensured uniformly. For example, when the pair of protrudingparts 104 b 1 and 104 b 2 are inserted into the open suction flowchannel groove 103 b 1 and the open discharge flow channel groove 103 b2, respectively, entrance regulating surfaces 104 a 1 and 104 a 2 of thepair of lid plates 104H and 104D abut on abutting surfaces 103 a 1 and103 a 2, respectively, thereby regulating the insertion (entrance)position of the protruding parts.

The sealing ring 241 b or 242 b does not receive a compressive force inthe stacked direction from the upper plate 103 and the pair of lidplates 104H and 104D. For example, any force that makes the upper plate103 and the pair of lid plates 104H and 104D separated in the stackeddirection from the sealing ring 241 b and 242 b is not applied to theupper plate and the lid plates. Accordingly, since a compressive forcethat is uniform as a whole is applied to the piezoelectric vibrator 30from the stacked direction, vibration of the piezoelectric vibrator 30is also uniformly generated in the stacked direction. Therefore, theoperation of the piezoelectric vibrator 30 can be stabilized, and afluid can be generated efficiently.

The present embodiments are aimed at the seal structure, which ensuresthe liquid tightness of the suction flow channel and discharge flowchannel of the above embodiment, with high durability. The lowerhousing, the umbrella, or the piezoelectric vibrator only shows anexample. Accordingly, although the umbrella is illustrated as a checkvalve, check valves other than the umbrella can also be used, and anelectrostrictive vibrator may be used instead of the piezoelectricvibrator. Further, the present invention can also be applied to a2-valve type diaphragm pump, i.e., a pump in which a pump chamber isformed only below a piezoelectric vibrator, and any pump chamber is notprovided above the piezoelectric vibrator (an umbrella is not provided).

According to the present embodiments, in a 4-valve diaphragm pump, theliquid tightness of the connecting parts of the flow channels formedover the upper housing and the lower housing can be ensured with highreliability and durability. The liquid tightness of the suction flowchannel and discharge flow channel formed in the upper housing can beensured with high reliability and durability.

1. A diaphragm pump comprising: an upper housing, diaphragm, and lowerhousing; recessed parts thatare respectively formed in the surfaces ofthe upper and lower housings opposing the diaphragm to define an upperpump chamber and a lower pump chamber above and below the diaphragm; asuction port and a discharge port that are formed in the lower housingto communicate with the lower pump chamber; branch channels that areformed in the lower housing and the upper housing to communicate thesuction port and the discharge port with the upper pump chamber;suction-side check valves that are provided between the suction port andthe upper pump chamber and between the suction port and the lower pumpchamber; and discharge-side check valves that are provided between thedischarge port and the upper pump chamber, and between the dischargeport and the lower pump chamber, wherein the branch channels include atleast one hole, a protruding cylindrical part fitted into the hole, anda sealing ring disposed in an annular gap formed between the hole andthe protruding cylindrical part such that a compressive force isgenerated in the radial direction of the sealing ring.
 2. The diaphragmpump according to claim 1, wherein the upper housing includes a pumpchamber plate that is stacked on the diaphragm and has the recessedpart, and a blind plate stacked on the pump chamber plate.
 3. Thediaphragm pump according to claim 2, wherein a pair of inter-platesuction flow channels and an inter-plate discharge flow channel thatcommunicate the suction port and the discharge port with the upper pumpchamber and that constitute parts of the branch channels are formedbetween the pump chamber plate and the blind plate.
 4. The diaphragmpump according to claim 3, wherein the inter-plate suction flow channeland the inter-plate discharge flow channel includes a pair of protrudingparts formed in any one of the pump chamber plate and the blind plate.5. The diaphragm pump according to claim 4, wherein a pair of recessedgroove parts that are formed in the another pump chamber plate and theblind plate to allow the pair of protruding parts to fit thereinto. 6.The diaphragm pump according to claim 5, wherein a pair of sealing ringswhich are disposed in a pair of closed curve gaps between the pair ofprotruding parts and the pair of recessed groove parts such that acompressive force are generated radially.
 7. The diaphragm pumpaccording to claim 1, wherein the upper housing is composed of an upperplate stacked on the diaphragm and a pair of lid plates.
 8. Thediaphragm pump according to claim 7, wherein the upper plate is formedwith recessed parts that are opened to the front and back of the upperplate to form the upper pump chamber.
 9. The diaphragm pump according toclaim 8, wherein a pair of open suction flow channel grooves and an opendischarge flow channel groove that constitute parts of the branchchannels that communicate the suction port and the discharge port withthe upper pump chamber, any one of the upper plate and the pair of lidplates is formed with protruding parts corresponding to the open suctionflow channel groove and the open discharge flow channel groove.
 10. Thediaphragm pump according to claim 9, wherein the other one of the upperplates and the pair of lid plates is formed with recessed groove partsto allow the pair of protruding parts to fit thereinto.
 11. Thediaphragm pump according to claim 9, wherein a pair of sealing rings areinterposed between the protruding parts and the recessed groove partssuch that a compressive force is generated radially.
 12. The diaphragmpump according to claim 2, wherein the protruding parts, the recessedgroove parts, and the sealing rings are elliptical.
 13. The diaphragmpump according to claim 3, wherein the protruding parts, the recessedgroove parts, and the sealing rings are elliptical.
 14. The diaphragmpump according to claim 1, wherein a compressive force in the stackeddirection of the upper housing, the diaphragm, and the lower housing isnot applied to any of the sealing rings.
 15. The diaphragm pumpaccording to claim 1, wherein the at least one hole is formed in theupper housing.
 16. The diaphragm pump according to claim 1, wherein theat least one hole is formed in the lower housing.